This
section discusses characteristics, trends, issues and proposals for action
in relation to water supply, drainage, sewage collection and treatment and
solid waste disposal. As part of this
exercise a number of meetings and consultations were held with representatives
of a number of central government Ministries and agencies. These consultations are continuing and a list
of those carried out to date are shown in Annex 1.
Water
for Greater Port of Spain can be obtained from several sources although the
bulk comes from the Caroni Arena water treatment works. Other sources that
supply water to the area include the Maraval, Hollis, North Oropouche and
a number of minor water treatment works and several groundwater sources including
El Socorro, Valsayn, Savannah and Four Roads.
There is a reasonably robust water transmission system that feeds water
in to Port of Spain and it is believed that there is sufficient conveyance
capacity to meet the water demands of the study area for the foreseeable future.
In
practice however, water supply to many parts is supplied for a limited number
of hours on account of the various source works having inadequate capacity
to meet the water demands of the nation as a whole. Several areas, particularly
in the upper reaches of the valleys leading into the Northern Range suffer
from poor pressures and infrequent service. There are still some communities
within the study area that do not have a pipe-borne water supply at present,
although it is understood that WASA’s North Water Project will address some
of these deficiencies. Areas that
currently have no pipe-borne supply include Upper Gonzales, Upper Perigod
Road, Fort George Road and Waterhole Road on Fort George Hill.
In
comparison to other parts of the country the Port of Spain area is well served
by water storage facilities and there appears to be sufficient overall storage
volume to meet the water balancing needs necessary to satisfy diurnal variations
in water demand. However, there are some pressure zones that have insufficient
storage capacity and studies carried out by Halcrow in 1995/6 suggested that
an additional 26Ml of water storage volume should be provided at Maraval,
Dundonald, Hololo, St Barbs, Redhill and Morvant with a further 5Ml needed
by 2015. Sites for the construction of these facilities should be reserved.
Many
of the secondary and tertiary distribution systems within Port of Spain area
are hydraulically or structurally inadequate and there is a need to reinforce
the network to allow all customers to receive a satisfactory level of service
and to reduce leakage levels. WASA has a programme of pipeline works and will
install new pipelines as funds become available.
The
current North Water Project is addressing some of the deficiencies. Where
there is an intention to redevelop an area it would be prudent to take the
opportunity to refurbish, replace or reinforce the water mains at the same
time.
Although
there are some deficiencies with the source capacity and distribution systems
these are generally the result of a historical lack of commitment to capital
expenditure and maintenance and could be reasonably readily resolved once
the necessary funding and resources are made available.
Flood
prone areas within the study area fall into three broad categories;
·
Areas
where flooding is caused when natural drains first enter the formal drainage
system e.g. on entering the paved drains at Bournes Road, Eckel Avenue and
where the Maraval River enters the built up area at La Seiva. At these points,
water borne debris tends to lodge against structures, causing the channel
to be blocked.
·
Locations
where the channel gradient abruptly gets to be less steep. This generally
occurs at the transition between old land and more recently reclaimed land,
such as along the Western Main Road in Cocorite, along Wrightson Road, South
Quay, along the Eastern Main Road and notably where the Malick River flows
out of the Northern Range onto the plain. The St. Ann’s River noticeably silts
up south of South Quay, whereas the concrete channel bottom is quite clean
north of South Quay.
·
Locations
that are very near to the level of high tide. This is mainly the case near
the western end of Independence Square.
The
capacity of the major channels in the study area is assessed to be about adequate
for their hydraulic design load. The St. Ann’s River will require minor upgrading
from South Quay going down-river[i].
The flood problems that are experienced are then predominantly a reflection
of the fact that debris and silt in the drains decrease their capacity. This also is felt to apply to a large degree
to the smaller local area drains.
(Unplanned) development of steep slopes and
areas upstream of the formal drainage system contribute to increased flood
flows and, more importantly, to increase removal of debris and sediment that
blocks channels lower down.
The
issue of managing the use of steep slopes in a more responsible manner was
the subject of a watershed management study for the Ministry of Agriculture.
This study recognised the need for halting the removal of vegetation and other
practices that increase flood flows and removal of soil from these slopes.
In
many instances the discharge capacity that is available is far below the design
capacity, due to lack of maintenance. The poor maintenance that occurs is
the more urgent problem, as the drainage system is not designed to facilitate
maintenance. (Difficult access to channels, flat-bottomed channels which encourage
sedimentation when flood-flows recede).
An
area east of the St. Ann’s River and south of the Eastern Main Road lies below
the flood level in the St. Ann’s River. This area drains to a pump station
adjacent to the St. Ann’s River, west of Abattoir Road. The efficacy of the
system is impaired by the fact that the pumps are not automated (or manned on a 24 hour basis). The capacity of the channels approaching the
pump-station is less than the pump capacity.
The clogging that frequently occurs in these approach channels further
exacerbates this lack of capacity.
The
1983 Port of Spain Drainage Study recommended that this pump-system be upgraded
and that two additional pump stations be installed to remove water from the
Western End of Charles Street and from Lower Murray Street. The ground level at these three locations is
2.85 m, 1.5 m and 2.10 m respectively. (All
levels above mean sea level).[ii].
The existing pump station east of the St. Ann’s River serves an area that
is only 0.9 m above mean sea level (South Quay east of St. Ann’s River). High tide design conditions that inform the
Port of Spain Drainage Study were taken as 1.6 m above Chart datum.[iii]
. Chart datum, the reference level
for tides and nautical charts = the lowest astronomical tide (+ 0 chart datum).
Mean Sea Level is + 0.7 m above chart datum.[iv]. The design tide level is then 0.9 m above mean
sea level.
The
majority of the study area is served by sewers that drain sewage to the Beetham
sewage treatment works (STW) although there is a private sewerage system within
the Fairways development in the Maraval valley. The principal unsewered areas
are the planned settlements above La Seiva Road in Maraval and Morvant and
the largely unplanned settlements within Laventille and Sealots.
Residences
in the currently unsewered areas generally have on-plot septic tanks for sewage
treatment although the poorer areas utilise pit latrines or cesspits. Unfortunately
the majority of these residences are situated on steep slopes where the use
of septic tanks, pit latrines and cesspits can create a nuisance and health
hazard for downhill residents on account of seepage of partially-treated effluent
through the hill faces.
It
has been reported that some of the lower-income residents do not even have
pit latrines and, presumably, and in these and areas not served by sewers,
grey water is generally discharged to open drains, presenting a nuisance to
downhill residents as well as odour and mosquito hazards.
Solid
waste is collected from most parts of the planned urban areas of Greater Port
of Spain three times a week. However, there are substantial areas, primarily
in the northern hillside developments and Laventille that only have their
garbage collected once a week at best, and several difficult to reach parts
of these settlements have no access to regular collection services.
There
is a common practice of putting garbage bags out into local communal storage
bunkers and bins on a daily basis and consequently rubbish may be stockpiled
locally for several days before it is collected. During this time vagrants
and animals rummage through the rubbish and spread it about, making collection
extremely difficult and aggravating the pollution and health hazards associated
with storing waste that is awaiting collection.
Another
problem that has been identified with the current practice of providing communal
waste bins is that they are frequently set on fire, either maliciously or
with the intention of alleviating odour problems, which then creates smoke
and smell nuisances and also damages the bins.
All
solid waste collected in the study area is disposed of to the Beetham waste
disposal landfill site on the south of Beetham Highway. The site is poorly
designed and inadequately managed. Frequent fires occur on the site, either
through spontaneous combustion or, more frequently, through scavengers burning
cable insulation in order to salvage copper. At least once a year these fires
get out of control and create a very serious air pollution problem for Port
of Spain and residents along the east-west corridor.
There
have been numerous recommendations that the site should be closed down and
the Solid Waste Management Company Limited (SWMCoL) have proposed that all
waste should be transported to Forres Park for disposal with the Beetham site
converted to a recycling and transfer station. It is understood that there
is a proposal before the Ministry of the Environment to this effect.
The
Trinidad and Tobago Electricity Commission (T&TEC) has advised that there
should be no difficulty meeting the electricity demands for any residential,
institutional, commercial or industrial developments that may occur in the
Greater Port of Spain area in the foreseeable future. Where a development
necessitates a significant reinforcement of the power transmission system
to be made, T&TEC would require a capital contribution from the developer
but most general in-fill type development can be readily accommodated.
All
of the study area is capable of being served by the existing installations
although there are some residents who are not currently connected and there
is some resistance or inability to pay for service in some of the poorer areas.
Historically, T&TEC required a prospective customer to produce land deeds
to confirm that they owned the land on which the property was situated. This
requirement has now been relaxed at the behest of the Government where the
applicant is living on state-owned land.
Much
of the high voltage transmission network within the central part of Port of
Spain is laid underground and T&TEC is currently embarking on a programme
of under-grounding all cables as replacement of cables is required. Currently
there are no plans to install major new transmission cables within the Greater
Port of Spain area.
The
National Gas Company of Trinidad and Tobago Limited (NGC) has advised that
there are two 16”gas lines which run along the Beetham Highway (one either
side) with one continuing along Wrightson Road and the other following Dock
Road before they terminate at the Port of Spain power station.
An
8”, reducing to 6”, pipeline runs off the 16” pipeline in the docks and follows
the T&TEC cooling water outlet channel and the seaward side of the Audrey
Jeffers Highway to Cocorite. The only other significant gas line is a 4” main
that is connected into the 8”/6” pipe on east bank of the Maraval River. This
runs along the river, past Fatima College, around King George V Park, through
Jackson Square and then around the inside south-side of the Savannah to the
Hilton Hotel. This last pipeline runs under lower pressure (100psi) than the
other pipelines (300psi) with the pressure reducing station being situated
near to the Highway Bridge over the Maraval River.
NGC
currently serves relatively few customers and no domestic users. Main customers
in Port of Spain include T&TEC, Peakes Marine and Hilton. They believe
that there is a large potential market for using natural gas for air conditioning
plants but take-up has been slow on account of the higher capital cost of
the air conditioning equipment, despite pay-back periods being only three
or so years. NGC believe that the existing pipelines feeding into and around
Port of Spain will be adequate to meet any foreseeable demand and they have
no plans for constructing additional pipelines.
WASA
has recently embarked upon a programme of well drilling that they anticipate
will provide between 39 and 77Mld of additional potable water for the country
and alleviate some of the current water supply deficiencies.
There
had been plans to develop a new run-of-river intake source on one of the rivers
in the Northeast of Trinidad, probably on the Matura River, but this proposal
appears to have been suspended in favour of drilling wells in the Matura River
bed. A desalination facility is currently under construction in the Couva
area that is intended to ultimately produce approximately 100Mld of treated
water for sale to customers in the Point Lisas Industrial Area.
However
this plant will not permit additional water to be released from existing sources
for use by other consumers as the water demand in the Point Lisas area is
anticipated to rise by 100Mld over the next 5-10 years.
Once
the well developments are on-line there should be approximately 5-10% more
water available for consumers outside of the Point Lisas Industrial Estate.
MOW
Drainage Division basically deals with drainage but it is understood that
there are no major works planned to address the major issues. The following
minor works are however programmed:
·
La
Seiva Bridge Reconstruction (1997/8 design);
·
Beetham
Estate Drains (John John area studies 1999 implement up to 2006);
·
Lady
Hochoy Drain (Cocorite walling works);
·
Malick
River (upstream of 7th Av. to Lady Young) Studies 1997 implement
walling works TT$ 50,000;
·
Outside
of the plan area of Greater Port of Spain, but impacting on the Malick River,
there are plans for works on the Mon Repos Drain (Never Dirty).
·
Maraval
river repairs (TT$ 90,000).
·
Local
Area Drainage along sewer traces.
The
Port of Spain City Corporation has embarked on a programme of leasing the
sewer traces to the adjacent owners, to relieve itself of the maintenance
responsibility that these traces present. However, the terms and conditions
of these lease arrangements warrant careful attention to ensure that the new
use of these sections of land does not impact negatively on surface drainage.
The
responsibility for implementing and maintaining the drainage system in the
Greater Port of Spain area is spread over various agencies, which lack a common
framework or clear and rational division of responsibilities.
These
are:
·
Drainage
Division (M.o.W.)
·
P.o.S.
City Council
·
San
Juan/Laventille Regional Corporation
·
Diego
Martin Regional Corporation
·
Ministry
of Agriculture’s Watershed Management programme.
·
The
Land Settlements Agency (Ministry of Housing & Settlements) who are responsible
for squatter regularization.
The
Drainage Division has a stated policy to conserve the existing runoff regime.
Developers are required, as an approval condition, to estimate the pre-development
response to a (20 year) design storm. The post-development situation must
then show how to achieve a response to the same design storm that does not
exceed the pre-development response.
This
seems to have potential for problems as over time there will be nothing to
stop the owner either failing to maintain the on-plot storage or paving it
over.
It
may be preferable to request developers to contribute into a fund at a rate
depending upon the size of the development and the area that is paved/covered
which can then be used for provision for flood alleviation ponds or similar
facility to serve groups of properties.
The
Master Plan should incorporate a drainage structure plan for gradual completion/infilling
by developers as new sites are constructed. This structure plan should seek
to:
·
Identify
areas at risk of flooding and capable of being used to store flood water –
these areas should not be developed unless temp storage capacity afforded
by them can be provided elsewhere.
·
Identify
areas that need to be protected from erosion (eroding gullies). In protecting these areas by slowing downs
flood flows, substantial detention storage can also be achieved
·
Identify
areas that are difficult to drain and avoid passing upstream water through
these areas.
·
Identify
areas inadequately drained but capable of being drained if pipes, culverts
or channels are upgraded.
·
Ensure
that ultimately the fully developed area will not respond less favourably
to the design storm than obtained in the pre-development situation.
From
a perspective of safety and aesthetics it is recommended that ponds be designed
for level fluctuations that are designed to not exceed 1 to at most 1.5 m.
To
minimise clogging the outflow it is recommended that outflow is controlled
by a VEE-shaped notch with sides at 45° to the vertical. Flows should approach
the outflow notch through a trash rack that has an available flow-through
surface not less than five times the cross-sectional area of the outflow control.[v].
The
trash rack should slope upwards at an angle to a horizontal grille where debris
can be collected, that can support maintenance personnel and from which debris
can be easily raked into a wheeled debris container. The metal bars that comprise
the Grille are to be oriented to facilitate raking debris from the grille.
It
is proposed to design detention ponds to so that the peak-flow in response
to the design storm is 30 litres/second/Ha. of drainage area. Both the St.
Ann’s and Maraval Rivers have a capacity/area ratio of 30 L/S/Ha. [vi]
Together
with the desire to avoid using small outflow openings that clog easily, the
proposed permissible water-level fluctuation indicates that ponds should serve
areas of 40 to 100 Ha.
It
is recommended that the area that is inundated frequently be landscaped as
a wetland or a permanent water-pond, linked to environmental and conservation
programmes. Permanent water ponds need to be well aerated. Aeration may be
achieved if the pond serves a perennial stream by guiding the inflow to cascade
over adequately dimensioned broad-crested weirs or by operating a waterspout-pump. An outflow control should also be installed
to permit complete evacuation of the facility.
Due attention must be given to facilitating removal of sediment.
Check
dams are (small) dams placed in steep gullies to break the speed of water
flowing down these gullies in order to break the destructive force of fast
flowing water. Checkdams serve to halt further erosion of gullies and to promote
deposition of sediment on the upstream side of the Gullies. If the checkdams
are effective they will eventually transform the gullies in which they are
installed to a series of steps.
On
steep slopes the risk of inundation does not exist. The major concerns with
respect to surface runoff centre on:
·
Avoiding
erosion and destruction of infrastructure by the forces of swiftly flowing
water.
·
Avoiding
flooding in the downstream reaches due to accelerated runoff.
Checkdams
are effective in maintaining low-flow velocities as well as temporarily storing
significant volumes of water. Checkdams can also be installed at a fraction
of the cost that would be required for installing similar discharge and storage
capacity in traditional concrete structures.
Checkdams
may be installed as a pile of boulders placed across a gully or as a palisade
of trees or stakes that will readily catch and grow to healthy trees in the
ambient environment. Trees and boulders
may be combined as a line of boulders with a palisade of stakes in a line
touching the upstream side of the boulders. Checkdams are to be installed,
starting at the upstream limit of a catchment, working in a downstream direction.
Checkdams
cannot be installed in one construction operation, but will require ongoing
maintenance and adjustment over a long period.
The overall costs are however significantly lower than costs for a
drain installation of comparable capacity in concrete. In fact, the costs that are associated with traditional construction
are basically prohibitive so that in steep terrain checkdams are the only
realistic option for managing surface runoff in low cost housing development.
Checkdams will form a barrier for water-borne debris and are consequently absolutely unsuited for an environment where solid waste is not ef